Anyone know when Sun plans to release 1.6 for Mac? I couldn't find an estimated date anywhere.

According to this post on the apple lists, the Java SE 6.0 Developer Preview release is out now for Intel and PowerPC based Macs. It's based on the 1.6 Beta version (currently the latest) of Java.
I think that you do need to have an Apple Developer Connection account though.

Sun doesn't release JVMs for Mac, Apple does.
And they typically require you to buy an operating system upgrade to get them.